[PATCH] D76388: [SelectionDAG] When splitting gathers/scatters in type legalization, set MMO size to UnknownSize

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: efriedma, RKSimon, spatel.
Herald added a subscriber: hiraditya.

Gather/scatter don't access one memory location, they access multiple disjoint locations. So using a fixed size isn't accurate. But we don't have a way to represent the true behavior so just use UnknownSize.

Previously we "split" the memory VT and use that size for the MMO of each half. But the memory VT is scalar so splitting usually just returned the original scalar VT, but on 32-bit X86 if the scalar VT was i64 it probably returned i32?


https://reviews.llvm.org/D76388

Files:
  llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp


Index: llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -20,6 +20,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "LegalizeTypes.h"
+#include "llvm/Analysis/MemoryLocation.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
@@ -1627,11 +1628,6 @@
       std::tie(MaskLo, MaskHi) = DAG.SplitVector(Mask, dl);
   }
 
-  EVT MemoryVT = MGT->getMemoryVT();
-  EVT LoMemVT, HiMemVT;
-  // Split MemoryVT
-  std::tie(LoMemVT, HiMemVT) = DAG.GetSplitDestVTs(MemoryVT);
-
   SDValue PassThruLo, PassThruHi;
   if (getTypeAction(PassThru.getValueType()) == TargetLowering::TypeSplitVector)
     GetSplitVector(PassThru, PassThruLo, PassThruHi);
@@ -1646,7 +1642,7 @@
 
   MachineMemOperand *MMO = DAG.getMachineFunction().
     getMachineMemOperand(MGT->getPointerInfo(),
-                         MachineMemOperand::MOLoad,  LoMemVT.getStoreSize(),
+                         MachineMemOperand::MOLoad, MemoryLocation::UnknownSize,
                          Alignment, MGT->getAAInfo(), MGT->getRanges());
 
   SDValue OpsLo[] = {Ch, PassThruLo, MaskLo, Ptr, IndexLo, Scale};
@@ -2376,13 +2372,10 @@
   SDValue Index = N->getIndex();
   SDValue Scale = N->getScale();
   SDValue Data = N->getValue();
-  EVT MemoryVT = N->getMemoryVT();
   unsigned Alignment = N->getOriginalAlignment();
   SDLoc DL(N);
 
   // Split all operands
-  EVT LoMemVT, HiMemVT;
-  std::tie(LoMemVT, HiMemVT) = DAG.GetSplitDestVTs(MemoryVT);
 
   SDValue DataLo, DataHi;
   if (getTypeAction(Data.getValueType()) == TargetLowering::TypeSplitVector)
@@ -2411,18 +2404,13 @@
   SDValue Lo;
   MachineMemOperand *MMO = DAG.getMachineFunction().
     getMachineMemOperand(N->getPointerInfo(),
-                         MachineMemOperand::MOStore, LoMemVT.getStoreSize(),
+                         MachineMemOperand::MOStore, MemoryLocation::UnknownSize,
                          Alignment, N->getAAInfo(), N->getRanges());
 
   SDValue OpsLo[] = {Ch, DataLo, MaskLo, Ptr, IndexLo, Scale};
   Lo = DAG.getMaskedScatter(DAG.getVTList(MVT::Other), DataLo.getValueType(),
                             DL, OpsLo, MMO, N->getIndexType());
 
-  MMO = DAG.getMachineFunction().
-    getMachineMemOperand(N->getPointerInfo(),
-                         MachineMemOperand::MOStore,  HiMemVT.getStoreSize(),
-                         Alignment, N->getAAInfo(), N->getRanges());
-
   // The order of the Scatter operation after split is well defined. The "Hi"
   // part comes after the "Lo". So these two operations should be chained one
   // after another.


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